Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds two real traits beyond that — output is deterministic and no files are written — but says nothing about what the returned skeleton contains, what gets echoed into planningContext, or whether acceptedDesign affects output (that detail lives only in the schema).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences, front-loaded with the core action and followed by the exclusion. No filler, no restatement of the title.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 8 parameters, a nested object, and no output schema, the description carries extra responsibility for describing the return value, yet it never says what a VideoSpec skeleton contains or that acceptedDesign flows into planningContext for later steps. The rich schema compensates for inputs but not for the missing output picture.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, including nested acceptedDesign fields and template/mediaSrc semantics, so the schema carries the parameter burden. The description contributes nothing about parameters (templateId, acceptedDesign, mediaSrc are all explained only in the schema), which matches the baseline 3.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb+resource: 'Return a deterministic VideoSpec skeleton' tells the agent exactly what is produced, and the negative clause ('does not generate creative copy or write files') implicitly separates it from siblings like create_video_brief and propose_video_storyboard. It stops short of naming an alternative, so it is clear but not fully sibling-differentiating.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied: 'does not generate creative copy or write files' signals this is a scaffolding step rather than a copywriting or render step, but there is no explicit statement of when to call it versus create_video_brief, prepare_video_template, or propose_video_storyboard. The agent must infer the placement in the workflow.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.